This invention relates to a detachable weaving frame that can be at least partly replaced on a continuously operating weaving machine without causing any interruption or any disturbance to the warp thread tension in the weaving zone.
Weaving frames are especially utilized in Jacquard weaving machines whereby each individual warp thread has a different yarn consumption during weaving. These weaving frames are disposed behind Jacquard weaving machines and are suited for carrying a large number of cross-wound spools or bobbins. This number corresponds to the total number of warp threads that are necessary for weaving pattern designs in different colors.
In the course of this text depth direction refers to warp direction, and width direction to weft direction.
In literature on the subject weaving frames are known that consist of a series of doors which extend in the depth direction and of which a number are disposed next to each other in the width direction of the weaving machine. Each weaving frame door is provided on both sides in height and depth with horizontal supporting spindles and thread guiding spindles. The bobbins are usually wound on a cardboard sleeve. This sleeve is placed on a cylindrical plastic sleeve, which is rotatable on the supporting spindle of the weaving frame. The bobbins can also be wound directly onto a plastic sleeve, so that they can be placed on the supporting spindle without additional plastic sleeve. The placing or changing of the bobbins in a weaving frame is carried out by a bobbin loader. For that purpose a passage is provided between each door of a weaving frame. The doors of a weaving frame can also be made rotatable or moveable.
From the bobbins that are placed in the weaving frame, the warp thread is pulled off (unwound) sideways and tangentially over the periphery. The pulled-off warp thread is first passed over a higher reversing guiding spindle located more toward the back and then brought back forward over the higher and forward lying reversing spindle of the forward lying bobbin. The warp threads run forward in the frame, into the throughput reed and the entrance grating, in order finally to come into the weaving zone of the weaving machine.
In order to exert a certain tension on the warp threads a first clamp or trammel is hung over the warp thread loop between the rear reversing guiding spindle and the bobbin in order to slow down the bobbin. A second clamp is hung between the front reversing guiding spindle and bobbin in order to pull back the warp thread out of the weaving zone. These two clamps or trammels that are hung on the warp thread together with the pulled-off loop form a type of band brake over the bobbin and thus establish a certain tension in the warp thread and also prevent the bobbin from unwinding on its own. The front clamp moreover also pulls the warp thread back out of the weaving zone. Hence the terms warp tensioning and pulling-back device of the weaving frame. With the known weaving frames this double function is exerted on and with the bobbin. This warp tensioning and pulling-back device is especially important with pile weaving machines for obtaining a uniform pile height and in order to make possible the interweaving of warp threads, which can take on more than two positions in the weaving shed.
When a Jacquard weaving machine has to be completely changed over to other weaving colors, the weaving machine is stopped in order to take all the bobbins out of the frame manually and in order to place new bobbins in the frame. This operation is labor-intensive and stopping the weaving machine signifies a certain production loss, with the result that the total output of the weaving machine will decrease the more color changes are performed.
Bobbin changes for the maintenance of a weaving frame or for changing certain neighboring pile warp threads can be performed on an operating weaving machine. The bobbin loader must moreover still work cautiously. Firstly both clamps or trammels have to be hung on the respective thread guiding spindle. Then the almost empty bobbin is taken off and the new bobbin is placed on the supporting spindle. A secure knot must be tied in order to connect the old warp thread to the new one and the remaining ends of the knot have to be cut off. Finally the clamps or trammels must be correctly placed and the warp thread must again be brought under tension by a small winding-up of the bobbin by a manual rotating movement. During the whole of the preceding operation the tension of the warp thread should not become too slack in order to avoid the thread keeper from coming into operation and thus interrupting the weaving, process. The tension may also not be too great or the warp thread will no longer fall into the lower position of the shed in the weaving zone so that in-weaving in the fabric becomes impossible and a so-called tension occurs. With pile weave this leads to a pulling closed of the fabric and a hole develops there after cutting through.
The weight of the bobbins that can be placed in a weaving frame is limited by the physical load capacity of the bobbin loader. In practical weaving this weight will not exceed 4 kg.
A device as described in BE no. 9500426 already offers the advantage that clamps or trammels are no longer necessary for maintaining the warp threads under tension and pulling them back out of the weaving zone. This device makes the replacement of a bobbin easier, but during the tying-together the tension on the warp thread between bobbin and recovery/tensioning device remains uncontrolled for a time and there are therefore possible causes of weaving faults. The slowing-down system of the bobbins presented there produces a tension in the warp thread that is dependent on the diameter of the bobbin. Furthermore this device is not suitable for a complete change of the weaving frame or a bobbin change with an automaton because the location of the unwound thread at the top of the bobbin is not set correctly and putting up the sleeve on a spindle requires a very accurate positioning of the bobbin sleeve in relation to the spindle. In the warp thread guiding spindles the various warp threads are not separated from each other. Separation gratings are however provided at certain distances in the weaving frame. But between these separation gratings the warp threads can become entangled with each other.